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AITKNDIX                                     283

siderations    of   this    kind    have    surest ed    the   alternative

e,nr,N   N

in which X stands for the acid radical (Blomstrand). The
nitrogen which combines with the acid radical is thereby quin-
quivalent, as m the ammonium salts. On the other hand, cli-
a/.obcn/,ene hydrate forms two isomeric potassium salts, one of
which is obtained by adding caustic potash to diazobenxcnc
chloride. This compound is unstable, and unites in the ordi-
nary way with phenols to form hydroxya/obciv/cne derivatives
(see Reaction 6, p. 103.1. The second one, which is obtained by
heatinj;1 the first to 130" with caustic potash, is very stable, and
does not combine directly with phenols (Sebraubcand Schmidt).
Other derivatives of dia/oben/ene exist in two forms, such as
the cyanide and sulphite. The difference has been explained
in two ways. According to one theory, the two potassium com-
pounds represent two different space configurations similar to
that of citraconic and mcsaconic acid (see p. 266) and the
oximes fsee p. 301), and are distinguished by the terms 'syn'
and l anti ' (1 lant/seh).
ruii;                                   c(.n,N
'I!                                          'II
KO.N                                     N.OK
Syii-lt'Mi.'i-M'-  li.i/MtaU' nf p.itnv,ium.        Anti-lx'iwnt' ilia/mate of potassium,
The  second   theory   ascribes   the   difference   to   structural
arrangement, and the compounds are termed dia/o- and   iso-
$  dia/.o compounds >' flamber^er).
(',;I1.,N:\()K.                            (:,,nBNK.NO.
r.i'ii.Titc tH.t/t.fatc ut" puias .iuin.              lii'ii/i-m- isodiaxotatc nf potassium.
li i-. now generally admitted that the dia/.o-salts of the
:.t mn;;cr acids, \vhi< h ha\'( only om^ representative, are most
'.atisfactorily represented by the u diaxonium," or Blomstrand
formula, and the salts are known as diazoniuni salts.
A few of the numerous changes which the diaxonium salts
undergo are illustrated in the series of reactions which follow
the preparation, and are amonjj the most important in organic
dutinjstty. Some of these reactions are carried out on a larger